/*
 * Copyright (C) 2006 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.jn.langx.escape;

import com.jn.langx.util.Preconditions;

import java.util.HashMap;
import java.util.Map;
import java.util.Map.Entry;

/**
 * Simple helper class to build a "sparse" array of objects based on the indexes that were added to
 * it. The array will be from 0 to the maximum index given. All non-set indexes will contain null
 * (so it's not really a sparse array, just a pseudo sparse array). The builder can also return a
 * CharEscaper based on the generated array.
 */
public final class CharEscaperBuilder {
    /**
     * Simple decorator that turns an array of replacement char[]s into a CharEscaper, this results in
     * a very fast escape method.
     */
    private static class CharArrayDecorator extends CharEscaper {
        private final char[][] replacements;
        private final int replaceLength;

        CharArrayDecorator(char[][] replacements) {
            this.replacements = replacements;
            this.replaceLength = replacements.length;
        }

        /**
         * Overriding escape method to be slightly faster for this decorator. We test the replacements
         * array directly, saving a method call.
         */
        @Override
        public String escape(String s) {
            int slen = s.length();
            for (int index = 0; index < slen; index++) {
                char c = s.charAt(index);
                if (c < replacements.length && replacements[c] != null) {
                    return escapeSlow(s, index);
                }
            }
            return s;
        }

        @Override
        protected char[] escape(char c) {
            return c < replaceLength ? replacements[c] : null;
        }
    }

    /**
     * Replacement mappings.
     */
    private final Map<Character, String> map;

    /**
     * The highest index we've seen so far.
     */
    private int max = -1;

    /**
     * Construct a new sparse array builder.
     */
    public CharEscaperBuilder() {
        this.map = new HashMap<Character, String>();
    }

    /**
     * Add a new mapping from an index to an object to the escaping.
     */
    public CharEscaperBuilder addEscape(char c, String r) {
        map.put(c, Preconditions.checkNotNull(r));
        if (c > max) {
            max = c;
        }
        return this;
    }

    /**
     * Add multiple mappings at once for a particular index.
     */
    public CharEscaperBuilder addEscapes(char[] cs, String r) {
        Preconditions.checkNotNull(r);
        for (char c : cs) {
            addEscape(c, r);
        }
        return this;
    }

    /**
     * Convert this builder into an array of char[]s where the maximum index is the value of the
     * highest character that has been seen. The array will be sparse in the sense that any unseen
     * index will default to null.
     *
     * @return a "sparse" array that holds the replacement mappings.
     */
    public char[][] toArray() {
        char[][] result = new char[max + 1][];
        for (Entry<Character, String> entry : map.entrySet()) {
            result[entry.getKey()] = entry.getValue().toCharArray();
        }
        return result;
    }

    /**
     * Convert this builder into a char escaper which is just a decorator around the underlying array
     * of replacement char[]s.
     *
     * @return an escaper that escapes based on the underlying array.
     */
    public Escaper toEscaper() {
        return new CharArrayDecorator(toArray());
    }
}
